The invention relates to a circuit for feeding fuel to an aircraft engine, and more particularly to a circuit delivering fuel for feeding combustion chamber injectors of the engine, and also for use as a hydraulic fluid for controlling actuators for actuating variable-geometry components of the engine.
As a general rule, the fuel feed circuit comprises a high pressure pump in the form of a positive displacement gear pump given by the engine via a gearbox known as an accessory gearbox (AGB). The flow rate delivered by the pump is not adapted to the real requirements of the engine and exceeds those requirements over a wide range of speeds of rotation of the engine. It is therefore necessary to add equipment to the outlet from the high pressure pump for metering the fuel delivered to the combustion chamber.
It is also known for the high pressure pump to be constituted by a variable-flow pump controlled by an electronic regulator module for the engine, thereby making it easier to adapt the delivered flow rate to the requirements of the engine.
In either case, a hydraulic actuator for actuating a variable-geometry component of the engine is controlled by a servo-valve having a high pressure admission inlet connected to the outlet from the pump and a low pressure exhaust outlet connected to a low pressure fuel feed line upstream from the pump.
When a sudden movement of the variable-geometry component is required, the fuel taken from the high pressure pump outlet leads to a disturbance in the feed to the injectors. This disturbance is made greater when the dynamic range of the metering equipment or of the assembly constituted by the variable flow rate pump and the electronic regulator module is small. This disturbance needs to be kept as small as possible since otherwise it can lead to engine malfunctions under certain flying conditions, such as pumping and engine flame-out.